Argyll Robertson Pupils. Argyll Robertson pupils are irregular and smaller than normal in darkness and demonstrate lack of the pupillary light reflex with preserved pupillary constriction during accommodation and convergence for near objects. These features, as in patients with large pupils with light-near dissociation, usually indicate a lesion in the rostral midbrain at the level of the posterior commissure.
Adie's Pupil. These tonic pupils are large and irregular in shape, poorly reactive to light, and indicate a lesion of the ciliary ganglion or short ciliary nerves. On slit-lamp evaluation, regional palsies of the iris sphincter are visible. These pupils have a hypersensitive constrictor response to administration of diluted muscarinic agonists, such as a 2.5 percent solution of methylcholine chloride or a 0.1 percent solution of pilocarpine. Adie's pupils are tonic pupils associated with reduced or absent tendon reflexes.
Horner's Syndrome. A unilateral small pupil is commonly due to underactivity of the ipsilateral sympathetic pathways. Miosis is commonly associated with ptosis (lid droop) due to sympathetic denervation of the tarsal muscle and facial anhidrosis (loss of sweating). This combination is known as Horner's syndrome. Oculosympathetic paralysis occurs ipsilaterally owing to (1) central lesions involving the hypothalamospinal pathways at the dorsolateral brain stem tegmentum (e.g., a lateral medullary infarct); (2) preganglionic lesions (e.g., compression of the sympathetic chain by a tumor in the apex of the lung); or (3) postganglionic lesions at the level of the internal carotid plexus (e.g., lesions of the cavernous sinus). Postganglionic Horner's syndrome does not result in facial anhidrosis because pupilodilator and sudomotor axons follow separate paths along branches of the internal and external carotid arteries, respectively.
Local instillation of drugs that affect sympathetic neurotransmission in the pupil helps to localize the lesion causing oculosympathetic paralysis. Cocaine hydrochloride (5 to 10 percent), which prevents NE reuptake, will not dilate a pupil that is miotic because of a lesion anywhere in the sympathetic pathway. The responsible lesion can be further localized by hydroxyamphetamine hydrobromide (Paredrine 1 percent), which is an indirect sympathomimetic agent that releases norepinephrine from the synaptic terminals, thus eliciting pupillary dilatation in patients with preganglionic but not postganglionic Horner's syndrome. Phenylephrine hydrochloride (Neo-Synephrine) is a direct alpha agonist that in a low concentration (1 percent) dilates the pupil only in patients with a postganglionic Horner's syndrome associated with denervation hypersensitivity of the pupil.
Facial flushing may result from the release of tonic sympathetic vasoconstriction, active sympathetic vasodilatation, increased parasympathetic activity via the greater petrosal nerve, and the release of vasoactive peptides. Gustatory sweating and flushing occur in the following conditions: idiopathic hemifacial hyperhidrosis associated with hypertrophy of the sweat glands; following bilateral cervicothoracic sympathectomy with reinnervation of the superior sympathetic ganglion by preganglionic sympathetic fibers destined for the sweat glands; after local damage to the autonomic fibers traveling with the peripheral branches of the trigeminal nerve (e.g., in parotid or submaxillary gland surgery or V3 zoster) with reinnervation of sweat glands and blood vessels by parasympathetic vasodilator fibers destined for the salivary glands; and accompanying peripheral neuropathies, most frequently diabetes mellitus. U
Sympathetic failure may produce loss of sweating and flushing as manifestations of Horner's syndrome. In contrast, the Porfour du Petit syndrome consists of a dilated pupil with flushing and hyperhidrosis due to sympathetic hyperactivity. This syndrome is seen in patients with sympathetic nervous system lesions, frequently following injuries of the neck that damage the sympathetic plexus around the carotid artery. The harlequin syndrome consists of a sudden onset of flushing and sweating on one side of the face. This disorder may be due to lesions in the contralateral central or peripheral sympathetic nervous system pathways. Attacks of cluster headache may be accompanied by ipsilateral signs of parasympathetic hyperactivity (lacrimation and nasal discharge), sympathetic overactivity (forehead sweating), and ocular sympathetic paralysis (miosis and ptosis). The mechanisms producing these phenomena have no widely accepted explanation. Changes in both the
sympathetic and the trigeminovascular pathways may be responsible for the autonomic features that accompany migraine and cluster headaches. y VASOMOTOR AND SUDOMOTOR DISORDERS OF THE LIMBS
Hyperhidrosis may be generalized or localized. Localized hyperhidrosis is rare and may occur with injury to the spinal cord (e.g., in syringomyelia), peripheral nerves (e.g., with partial median or sciatic nerve injury), or eccrine sweat glands. Perilesional hyperhidrosis may surround an anhidrotic region produced by a lesion of the sympathetic ganglia or rami. The axillary eccrine sweat glands are activated by thermal stimuli, whereas the palmar and plantar glands are activated by emotional stimuli. Primary or essential hyperhidrosis affects the axillary, palmar, and plantar regions and may be familial. Generalized hyperhidrosis may be secondary to infections, malignancies, or neuroendocrine disorders (e.g., pheochromocytoma, thyrotoxicosis, acromegaly, carcinoid, anxiety, hypotension, hypoglycemia, and cholinergic agents).y
Vasomotor disorders in the limbs include Raynaud's phenomenon, acrocyanosis, livedo reticularis, vasomotor paralysis, and erythromelalgia. Raynaud's phenomenon is the episodic, bilateral, symmetrical change in skin color (pallor, followed by cyanosis and terminating in rubor after rewarming) that is provoked by cold or emotional stimuli. This response is due to episodic closure of the digital arteries. There is, however, no consistent evidence of exaggerated sympathetic outflow to the skin. Raynaud's phenomenon may be associated with connective tissue disease (e.g., scleroderma, rheumatoid arthritis, psoriasis), occupational trauma (such as the use of pneumatic hammers, chain saws producing vibration), the thoracic outlet syndrome, the carpal tunnel syndrome, or certain drugs (e.g., beta blockers, ergot alkaloids, methysergide, vinblastine, bleomycin, amphetamines, bromocriptine, and cyclosporine). y
Acrocyanosis is a symmetrical distal blue discoloration, usually occurring below the wrists and ankles, that is due to arteriolar constriction and is aggravated by cold. In contrast, livedo reticularis is a vasomotor disorder that affects the extremities and the trunk and is due to vasospasm with obstruction of the perpendicular arterioles or stasis of blood in the superficial veins. It may be a benign disorder or may be associated with vasculitis, antiphospholipid antibodies (Sneddon's syndrome), connective tissue disease, hyperviscosity syndrome, thrombocythemia, and drugs (e.g., amantadine, quinine, and quinidine). y
Vasomotor paralysis may be seen in patients with lesions of the sympathetic pathways at the level of the spinal cord, preganglionic nerves, ganglia, or postganglionic nerves. Examples include surgical sympathectomy (e.g., for treatment of selective cases of hyperhidrosis, Raynaud's phenomenon, and reflex sympathetic dystrophy), trauma (e.g., carpal tunnel syndrome, ulnar nerve lesions), and tumor infiltration (e.g., Pancoast's tumor, malignant retroperitoneal disease).
Erythromelalgia is a painful acral erythematous condition that occurs with cutaneous warming and is associated with an intense burning sensation. It may occur in patients with small-fiber neuropathies. The mechanism may be activation of neurogenic flare by a polymodal C nociceptor axon and release of vasodilator and algogenic neuropeptides such as substance P. y
Reflex sympathetic dystrophy is a pain syndrome defined as a continuous burning pain, hyperpathia (exaggerated response to painful stimuli), and allodynia (perception of an innocuous stimulus as painful) in a portion of an extremity. This disorder is associated with signs of sympathetic hypoactivity or hyperactivity and usually follows minor trauma that does not involve major nerves. Causalgia is a similar syndrome that occurs after partial injury of a nerve or one of its major branches. Vasomotor and sudomotor instability, manifestations of sympathetic hyperactivity or hypoactivity, are commonly seen. Reflex sympathetic dystrophy is not a single pathological entity, but different central, peripheral, and psychogenic mechanisms may coexist in a particular case. Sympathetic blockade may be of benefit. y
Disturbances at different levels of the bladder control system result in the development of neurogenic bladder. Neurogenic bladders can be subdivided into two types: the reflex or upper motor neuron type, and the nonreflex or lower motor neuron type. The terms reflex and nonreflex denote the presence or absence, respectively, of bulbocavernosus and anal reflexes. The reflex type of neurogenic bladder includes the uninhibited bladder associated with lesions of the medial frontal region that results in urinary incontinence but not urinary retention because the detrusor-sphincter synergy is preserved. The automatic bladder results from lesions of the spinal cord that interrupt the pathway from the pontine micturition centers. An automatic bladder is associated with urgency, frequency, incontinence, and urinary retention that is due to detrusor-sphincter dyssynergia. The lower motor neuron type of neurogenic bladder, such as that occurring with lesions of the cauda equina or peripheral nerves, is characterized by incomplete bladder emptying, urinary retention, and overflow incontinence. y
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